X-ray imaging (fluoroscopy) is an important imaging modality for cardiac interventions. For providing a guidance of procedures that require more soft-tissue information, for example the treatment of structural heart disease, transesophageal echocardiography (TEE) information is employed TEE imaging, which is a form of ultrasound imaging, is able to show e.g. an interventional device and its surrounding anatomy simultaneously.
It has been proposed to complement X-ray imaging with live 3D TEE imaging. In this case, the drawback of X-ray images having poor tissue contrast is alleviated using soft tissue information from the 3D TEE images. For this purpose, the X-ray image and TEE images need to be registered. For example, an article by Jain et al., “3D TEE Registration with X-Ray Fluoroscopy for Interventionak Cardiac Applications”, Functional Imaging and Modeling of the Heart, LNCS vol. 5529, pp. 321-329, Springer (Heidelberg) 2009, describes registration with the aid of an electromagnetic tracking system.
When X-ray and TEE images are thus registered, there is a need to identify a view from the TEE data that optimally complements the X-ray image information.
WO 2007/049207 A1 discloses a system and a method for generating a number of standard 2D echocardiographic views from 3D image data acquired in respect of a subject. A medical practitioner positions a 3D probe so that one visualization plane corresponds to a standard 2D view and then pre-calculated relative coordinates are used to automatically locate and generate other standard 2D views. Alternatively, a landmark extraction algorithm is used to identify specific features, from which the respective visualization planes can be located and the standard 2D views generated.
Locating an optimal viewing plane for an interventional device (valve clips, plugs . . . ) in 3D TEE images is particularly challenging and time consuming, disrupting clinical workflow and increasing the chance of miscommunication. So far, defining such viewing plane has required manipulating the 3D TEE images themselves. For example, a user interface may be provided to allow rotating and cropping (i.e. defining a cut plane) of these images. Such actions have to be carried out manually, repeating them as often as needed until an optimal plane is found. Typically, multiple rotating and cropping actions are required before an acceptable result is obtained. Often, in addition, fine adjustments of the 3D probe position and orientation will be required as well.
Finally, the appropriate viewing plane for a device can change throughout the procedure, depending on whether a device is being positioned, deployed or assessed for function. Thus, several ideal viewing planes for a device could be required over the course of a single interventional procedure. Thus, it may be required to interrupt the procedure to repeat the tedious process of finding an optimal viewing plane.